This invention relates to cartridge dispensing guns for cartridges of the kind containing two separate components.
Disposable cartridges containing various products such as adhesives, sealants and the like are well known throughout many industries. The contents are usually expelled from the cartridges by means of a gun that acts against a piston contained within the cartridge to expel the contents from an aperture at the other end of the cartridge. The guns typically include a bed to retain the cartridge and a piston pusher mechanism, usually having a trigger to incrementally advance a piston pusher on the end of a rod that extends into the cartridge to bear against the piston. Standard single component cartridges typically have a diameter of around 46 mm.
It is also known to use coaxial cartridges which dispense two components in a selected ratio. These cartridges are effectively formed by two coaxially arranged compartments each containing one of the two components and having a separate piston for discharge of the component. The two components are typically components of epoxy or polyester which when mixed in a selected ratio cure to form to form a hardened material. In this type of cartridge the two components are expelled from their respective separate compartments, passed through a static mixer and then some form of mixer nozzle for direct application. The cartridge dispensing guns used with these two component cartridges have a pair of coaxially arranged piston pushers that are simultaneously advanced by the same mechanism.
A difficulty arises because different types of materials require differing ratios between the two components contained within the cartridges. This is achieved by adjusting the diameter of the inner compartment so that the appropriate volumetric ratio between the components expelled by the same amount of linear movement of the corresponding pistons is achieved. Component ratios of 2:1, 8:1, and 10:1 are in common use. Another difficulty arises because coaxial cartridges have different capacities this changing the external diameter of the cartridge. These all require different cartridge dispensing guns.
It is an object of this invention to provide an improved cartridge dispensing guns for cartridges of the kind containing two components.
According to the present invention, there is provided a manually operable cartridge dispensing gun for cartridges of the kind containing two components, said gun including a bed to captively retain the cartridge, a manually operable drive assembly to advance inner and outer concentrically arranged piston pushers against corresponding pistons in the cartridge, the outer piston pusher being dimensioned to bear against a circumferentially outermost piston in the cartridge and including a central aperture to accommodate the inner piston pusher of a first dimension for use with an inner piston of a cartridge having a first component ratio, said inner piston pusher being selectively reconfigurable to a second, reduced, dimension for use with an inner piston of a cartridge having a second component ratio.
In a preferred embodiment the inner and outer piston pushers form a pusher assembly and the inner piston pusher is reconfigured by removing an element of the pusher assembly. For example, the pusher assembly can include a rod that is advanced having a threaded end that receives a correspondingly threaded pusher. The end of the rod can be of a diameter selected to correspond to the second reduced dimension when the threaded pusher element is removed.
Preferably, the outer piston pusher takes the form of a circular ring.
In a preferred configuration the outer piston pusher is removable enabling the gun to also be used with standard single component cartridges.
In the preferred form of the invention a central rod aligned with the longitudinal axis of the cartridge is advanced by the drive assembly. The inner piston pusher is mounted to one end of the rod. The outer piston pusher is concentrically mounted with the inner pusher by means of two parallel extending rods that attach to the central rod adjacent the end remote from the cartridge. Preferably, guide slots are formed in an end plate on the bed of the gun to guide the parallel rods and maintain the position of the outer pusher with respect to the inner pusher. The guide slots are preferably open so that the parallel rods can be resiliently displaced and disengaged from the guide slots in the end plate.